wp_set_current_user( int $id, string $name = '' )

function wp_set_current_user($id, $name = '') {
	global $current_user;

	// If `$id` matches the user who's already current, there's nothing to do.
	if ( isset( $current_user )
		&& ( $current_user instanceof WP_User )
		&& ( $id == $current_user->ID )
		&& ( null !== $id )
	) {
		return $current_user;
	}

	$current_user = new WP_User( $id, $name );

	setup_userdata( $current_user->ID );

	/**
	 * Fires after the current user is set.
	 *
	 * @since WP-2.0.1
	 */
	do_action( 'set_current_user' );

	return $current_user;
}